What is Postman and what is it actually good for in 2026?

Postman in 2026 is best for: manual API exploration, quick contract sanity checks, sharing collections with backend/PM, and lightweight monitors. For real regression automation ship Newman in CI or (better) move to code — REST Assured / pytest+requests / Playwright APIRequestContext — where you get version control, PR review, and language tooling. So your senior is half right: not for the main automation suite; still gold for exploration and collaboration.